Various medical, industrial and graphic imaging applications require the production of very high quality images. One way to produce high quality images is through the use of a photothermographic processor. One type of photothermographic processor uses a thermally processable, light sensitive photothermographic film that typically includes a thin polymer base coated with an emulsion of dry silver or other heat sensitive material. This photothermographic film may take the form of short sheets, longer lengths or continuous rolls of photothermographic material. These sheets, lengths and rolls are often referred to as photothermographic elements.
A photothermographic processor generally includes a photothermographic element exposure system, a thermal processing mechanism and a cooling apparatus. The exposure system typically employs a laser scanner device that produces laser light that exposes the photothermographic element to form a latent image thereon. The thermal processing mechanism is used to thermally develop this latent image. To develop the latent image, the thermal processing mechanism heats the exposed photothermographic element to at least a threshold development temperature for a specific period of time to develop the image within the photothermographic element. Subsequently, the photothermographic element must be cooled by the cooling apparatus of the photothermographic processor to allow a user to hold the element while examining the developed image.
During cooling, the photothermographic element is susceptible to physical and image defects. These defects are primarily due to uneven cooling of the developed photothermographic element and dimensional changes that occur in the element during cooling. Uneven cooling across the developed photothermographic element and uncontrolled dimensional changes which occur during cooling cause thermal stresses and contraction or expansion within the element. These thermal stresses and contraction or expansion can cause physical and image wrinkles, streaks and/or spots (i.e., defects), in the developed photothermographic element, which can significantly affect the quality of the developed image.
In addition to the physical and image defects that can occur during cooling, a photothermographic element is also susceptible to physical and image defects caused in other ways. For example, physical and image defects can occur in the photothermographic element due to a speed mismatch, wherein an element transport mechanism of the cooling apparatus is moving at a speed different than the speed of a conveyance device of the thermal processing mechanism.
If the element transport mechanism of the cooling apparatus is moving at a speed slower than the speed of the conveyance device of the thermal processing mechanism, buckling of the photothermographic element can occur due to the excess buildup of the element in the cooling apparatus. Buckling of the photothermographic element within the thermal processing mechanism can result in uneven contact between heated development rollers of the thermal processing mechanism and the element during the development process. This uneven contact can cause underdevelopment of portions of the latent image, thereby resulting in image artifacts that adversely affect the quality of the developed image. Buckling of the photothermographic element within the cooling apparatus can result in uneven cooling of the element, resulting in image affecting physical defects within the photothermographic element and possible element jams.
If the element transport mechanism of the cooling apparatus is moving at a speed faster than the speed of the conveyance device of the thermal processing mechanism, slippage must occur between the photothermographic element and the element transport mechanism of the cooling apparatus, or between the element and the conveyance device of the thermal processing mechanism, or between the element and both of the transport mechanism and the conveyance device. This slippage of the photothermographic element can cause areas of high tension in the element in a down-web direction (i.e., parallel to the direction of travel of the photothermographic element). These areas of high tension can cause physical and image defects, such as wrinkles, in the photothermographic element during cooling of the element.
A photothermographic element is further susceptible to physical and image defects caused in other ways. For example, the element transport mechanism that moves the photothermographic element through the cooling apparatus generally takes the form of a pair of nip rollers. These nip rollers by their design nature, prohibit cross-web (i.e., perpendicular to the direction of travel of the photothermographic element) expansion or contraction of the photothermographic element. This prohibition of cross-web expansion and contraction of the photothermographic element can cause physical and image defects, such as wrinkles, in the element during cooling thereof. This type of defect is particularly acute when the width of the photothermographic element is large (i.e., in excess of 18"). In addition, the design nature of the nip rollers of the cooling apparatus requires that the photothermographic element enter the nip rollers relatively straight or a skew in the direction of travel of the element can occur. This directional skew of the photothermographic element can result in nonuniform contact between a cooling article of the cooling apparatus and the element during the cooling process. This non-uniform contact can result in uneven cooling of the photothermographic element, resulting in image affecting physical defects within the element and possible element jams.
There is a need for an improved apparatus and method for cooling thermally processed, photothermographic elements. In particular, there is a need for a photothermographic element cooling apparatus and method which sufficiently cools a developed photothermographic element to allow a user to hold the element for examining the developed image, and minimizes physical and image defects in the developed image that would adversely affect the image quality of the developed photothermographic element. In addition, the photothermographic element cooling apparatus and method should provide these features while offering acceptable cooling productivity, cost effectiveness, and ease of assembly and repair.